/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.master;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.zookeeper.ZKNodeTracker;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZNodePaths;
import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
import org.apache.hadoop.hbase.client.MasterSwitchType;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.ZooKeeperProtos.SwitchState;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.zookeeper.KeeperException;


/**
 * Tracks the switch of split and merge states in ZK
 */
@InterfaceAudience.Private
public class SplitOrMergeTracker {

    private String splitZnode;
    private String mergeZnode;

    private SwitchStateTracker splitStateTracker;
    private SwitchStateTracker mergeStateTracker;

    public SplitOrMergeTracker(ZKWatcher watcher, Configuration conf, Abortable abortable) {
        try {
            if(ZKUtil.checkExists(watcher, watcher.getZNodePaths().switchZNode) < 0) {
                ZKUtil.createAndFailSilent(watcher, watcher.getZNodePaths().switchZNode);
            }
        } catch(KeeperException e) {
            throw new RuntimeException(e);
        }
        splitZnode = ZNodePaths.joinZNode(watcher.getZNodePaths().switchZNode, conf.get("zookeeper.znode.switch.split", "split"));
        mergeZnode = ZNodePaths.joinZNode(watcher.getZNodePaths().switchZNode, conf.get("zookeeper.znode.switch.merge", "merge"));
        splitStateTracker = new SwitchStateTracker(watcher, splitZnode, abortable);
        mergeStateTracker = new SwitchStateTracker(watcher, mergeZnode, abortable);
    }

    public void start() {
        splitStateTracker.start();
        mergeStateTracker.start();
    }

    public boolean isSplitOrMergeEnabled(MasterSwitchType switchType) {
        switch(switchType) {
            case SPLIT:
                return splitStateTracker.isSwitchEnabled();
            case MERGE:
                return mergeStateTracker.isSwitchEnabled();
            default:
                break;
        }
        return false;
    }

    public void setSplitOrMergeEnabled(boolean enabled, MasterSwitchType switchType) throws KeeperException {
        switch(switchType) {
            case SPLIT:
                splitStateTracker.setSwitchEnabled(enabled);
                break;
            case MERGE:
                mergeStateTracker.setSwitchEnabled(enabled);
                break;
            default:
                break;
        }
    }

    private static class SwitchStateTracker extends ZKNodeTracker {

        public SwitchStateTracker(ZKWatcher watcher, String node, Abortable abortable) {
            super(watcher, node, abortable);
        }

        /**
         * Return true if the switch is on, false otherwise
         */
        public boolean isSwitchEnabled() {
            byte[] upData = super.getData(false);
            try {
                // if data in ZK is null, use default of on.
                return upData == null || parseFrom(upData).getEnabled();
            } catch(DeserializationException dex) {
                LOG.error("ZK state for LoadBalancer could not be parsed " + Bytes.toStringBinary(upData));
                // return false to be safe.
                return false;
            }
        }

        /**
         * Set the switch on/off
         * @param enabled switch enabled or not?
         * @throws KeeperException keepException will be thrown out
         */
        public void setSwitchEnabled(boolean enabled) throws KeeperException {
            byte[] upData = toByteArray(enabled);
            try {
                ZKUtil.setData(watcher, node, upData);
            } catch(KeeperException.NoNodeException nne) {
                ZKUtil.createAndWatch(watcher, node, upData);
            }
            super.nodeDataChanged(node);
        }

        private byte[] toByteArray(boolean enabled) {
            SwitchState.Builder builder = SwitchState.newBuilder();
            builder.setEnabled(enabled);
            return ProtobufUtil.prependPBMagic(builder.build().toByteArray());
        }

        private SwitchState parseFrom(byte[] bytes) throws DeserializationException {
            ProtobufUtil.expectPBMagicPrefix(bytes);
            SwitchState.Builder builder = SwitchState.newBuilder();
            try {
                int magicLen = ProtobufUtil.lengthOfPBMagic();
                ProtobufUtil.mergeFrom(builder, bytes, magicLen, bytes.length - magicLen);
            } catch(IOException e) {
                throw new DeserializationException(e);
            }
            return builder.build();
        }
    }
}
